EP1221783A1 - Remote feeding device for a terminal in a telecommunications network , concentrator and repeater with such a device - Google Patents

Abstract

A current measuring circuit determines whether incoming current to a concentrator (3) is greater than a threshold current. A resistor of the current measuring circuit has low resistance when the current is greater than the threshold value. A logic circuit (43) compares the voltage across the resistor with a threshold voltage to determine voltage drop across the resistor. Independent claims are included for the following: (1) Repeater; and (2) Concentrator.

Description

The present invention relates generally to a network of telecommunications, in particular a local computer network, for example of Ethernet type, or a telephone network. More specifically, the invention relates a device for remote supplying a terminal in such a network. classically, terminals connected to a local computer network (for example: personal computers, printers, etc.) are powered locally, by the sector. It is desirable that certain terminals be remotely powered, through the same link as the one used to send / receive data. It is further desirable that the remote feeding device can be installed in any point of the connection: either inside or outside a repeater, or hub, to allow easy addition to a already existing network.

One way of transmitting a remote supply current is to use two of the eight wires in the bond: four more of these eight wires are two pairs of wires used respectively to transmit and receive data. Another way, called by phantom circuit, consists in connecting the two terminals of a power generator respectively at the midpoints of a winding transformer connected to the data reception pair and a winding another transformer connected to the data transmission pair, in the remote power device. On the terminal side, the supply voltage is supplied respectively by the midpoints of a winding of transformer connected to the data reception pair and a winding another transformer connected to the data transmission pair.

• Quatre fils des huit fils sont séparés en deux paires pour respectivement transmettre et recevoir des données. Le terminal comporte un transformateur ayant un enroulement relié à la paire de réception, et un transformateur ayant un enroulement relié à la paire d'émission, chacun de ces enroulements ayant un point milieu qui peut être relié à un potentiel de référence via une résistance de faible valeur.
• Quatre autres fils, inutilisés, sont mis à la masse, souvent par l'intermédiaire d'une combinaison de résistances et de capacités, pour éliminer les éventuels courants de diaphonie induits par les signaux de données circulant dans les quatre premiers fils, et pour réduire les émissions électromagnétiques indésirables. Si on applique une tension d'alimentation relativement élevée, par exemple 48 Volts, sur cette combinaison de résistances et de capacités, ou sur les résistances reliées aux points milieux des transformateurs, l'intensité du courant circulant dans ces résistances peut les détruire, ainsi que les circuits d'émission-réception.

In both cases, remote powering the terminal via the local computer network has the drawback that the remote power supply device blindly powers a terminal. However, an RJ45 socket located at the end of the link can receive a terminal of a type other than a remote power terminal (for example a personal computer, a printer, etc.). There is a risk of damaging the electrical circuits of this terminal. In fact, the male RJ45 socket on a terminal is generally used in the following manner:

• Four wires of the eight wires are separated into two pairs to respectively transmit and receive data. The terminal comprises a transformer having a winding connected to the reception pair, and a transformer having a winding connected to the emission pair, each of these windings having a midpoint which can be connected to a reference potential via a resistor. low value.
• Four other unused wires are grounded, often through a combination of resistors and capacitors, to eliminate possible crosstalk currents induced by the data signals flowing in the first four wires, and to reduce unwanted electromagnetic emissions. If a relatively high supply voltage, for example 48 volts, is applied to this combination of resistors and capacitors, or to the resistors connected to the midpoints of the transformers, the intensity of the current flowing in these resistors can destroy them, thus than the transmit-receive circuits.

We are currently studying automatic identification methods for avoid any risk of damage if you connect a terminal that is not a terminal able to be remotely powered by the network.

• produire un signal de test, ou plusieurs signaux de test, sur au moins deux conducteurs d'une liaison destinée à relier le réseau local à un terminal distant, ce signal ayant une énergie telle que le terminal ne peut être endommagé en aucun cas ;
• détecter la présence d'un terminal distant téléalimentable, en détectant la présence d'un module d'identification placé dans le terminal distant, en dérivation sur la liaison, à partir du courant créé par le signal ou les signaux de test dans cette liaison ;
• envoyer un courant de téléalimentation dans cette liaison, si et seulement si la présence d'un terminal téléalimentable est détectée.

Such a method consists in:

• producing a test signal, or several test signals, on at least two conductors of a link intended to connect the local network to a remote terminal, this signal having an energy such that the terminal cannot be damaged in any case;
• detecting the presence of a remotely powered remote terminal, by detecting the presence of an identification module placed in the remote terminal, bypass on the link, from the current created by the signal or the test signals in this link;
• send a remote supply current in this link, if and only if the presence of a remote supply terminal is detected.

Such a method avoids any risk for the terminals because the remote supply current is only sent after having identified the terminal as being remotely powered. The intensity and duration of the signal or test signals are chosen so that the operation of detecting the presence of a remote power terminal, before the remote power supply, cannot cause any damage in the event that the terminal is not not a terminal capable of being remotely powered.

On the other hand, the remote power supply must be interrupted as soon as the terminal is disconnected from the link, as one could connect another at any time. Provision is therefore made to continuously detect the presence of a terminal during the remote supply, by measuring the intensity of the remote supply current. The remote supply device concludes a disconnection if it detects that the intensity of the current consumed becomes less than a predetermined threshold value (1 mA for example), during a time interval having a predetermined duration which is sufficient to ensure that there was a disconnection. It is known to measure an intensity by measuring the voltage across a resistor. For a comparator to reliably detect whether the voltage drop is above or below a threshold value, a voltage drop of at least 50 mV must be available, due to noise and voltage offset that could affect the voltage measurement circuit. This leads to using a resistor of at least 50 ohms, to detect if the intensity is greater than a threshold value of 1 mA.

In addition, it is necessary to measure the intensity of remote power to control a current limiter responsible for protecting the device from remote power supply, and the terminal, against an overcurrent. Maximum intensity admissible being typically 350 mA, a resistance of 50 ohms produced a voltage drop of 17.5 V and a dissipation of 6 W, which are not negligible.

A similar problem arises when making an interface card for subscriber line, for a telephone exchange. Such a card ensures the remote supply of a telephone terminal connected to the end of a line. It must detect the line seizure by detecting that the intensity of remote power supply becomes greater than a threshold value. If we want to be able connect different types of terminals, which consume very high currents different, to the same type of card, it is necessary that this card does not cause not a significant voltage drop when the terminal consumes an intensity much higher than the threshold value (in normal operation).

The object of the invention is to be able to detect whether a terminal consumes an intensity greater than at least a given threshold value, without interfering with the operation of a terminal if this terminal actually requires a very high intensity greater than this given threshold value, and avoiding a loss not negligible voltage and power in the remote supply device.

• un circuit résistif parcouru par le courant de téléalimentation,
• et des moyens pour comparer la tension aux bornes de ce circuit résistif avec une première valeur de seuil de tension,

   caractérisé en ce que ce circuit résistif présente une résistance variable en fonction de l'intensité qui le parcourt, cette résistance étant plus faible lorsque l'intensité est très supérieure à la première valeur de seuil d'intensité.The object of the invention is a remote supply device for a terminal in a telecommunications network, this remote supply device comprising a measurement device for determining at least if the intensity of the remote supply current is greater than a first value of intensity threshold, the intensity possibly taking a value much higher than this first threshold value; this measuring device comprising:

• a resistive circuit traversed by the remote supply current,
• and means for comparing the voltage across the terminals of this resistive circuit with a first voltage threshold value,

characterized in that this resistive circuit has a variable resistance as a function of the intensity which traverses it, this resistance being lower when the intensity is much greater than the first intensity threshold value.

The device thus characterized also causes a voltage drop negligible when the intensity is much higher than the intensity threshold value only when it is close to this intensity threshold value, because the reduction of the resistance presented by this device when the intensity becomes much higher than the threshold value tends to compensate for the increase in fall of tension due to increased intensity.

According to a particular embodiment, making it possible to determine whether the intensity of the remote supply current is greater than a first value of intensity threshold and to determine if this intensity is greater than one second intensity threshold value, which is higher than the first, the measurement further comprises means for comparing the voltage across the terminals of this resistive circuit with a second voltage threshold value; and this resistive circuit presents a variable resistance depending on the intensity which traverses it, this resistance being lower when the intensity is close to the second value of intensity threshold, only in the vicinity of the first intensity threshold value.

• une première résistance de mesure,
• une seconde résistance de mesure ayant une valeur inférieure à celle de la première,
• et un dispositif de commutation pour alternativement :
  • mettre la première résistance en série dans le circuit de téléalimentation, si le dispositif de commutation détecte que l'intensité est inférieure à une troisième valeur de seuil d'intensité, qui est comprise dans l'intervalle entre la première et la deuxième valeur de seuil d'intensité ;
  • ou mettre la seconde résistance en série dans le circuit de téléalimentation, si le dispositif de commutation détecte que l'intensité est supérieure à la troisième valeur de seuil.

According to a particular embodiment, this resistive circuit comprises:

• a first measurement resistance,
• a second measurement resistance having a value lower than that of the first,
• and a switching device for alternately:
  • put the first resistor in series in the remote supply circuit, if the switching device detects that the intensity is less than a third intensity threshold value, which is between the first and the second threshold value intensity;
  • or put the second resistor in series in the remote supply circuit, if the switching device detects that the intensity is greater than the third threshold value.

The device thus characterized easily provides good precision of comparison of the intensity with respect to the two intensity threshold values, because the resistance value of the resistive circuit is suddenly switched between two perfectly defined values.

The invention also relates to a repeater and a concentrator comprising such a remote supply device.

• La figure 1 représente le schéma synoptique d'une partie d'un exemple de réseau local comportant des concentrateurs et des répéteurs comportant chacun un exemple de réalisation du dispositif de téléalimentation selon l'invention.
• La figure 2 représente le schéma synoptique d'un concentrateur comportant un exemple de réalisation du dispositif de téléalimentation, et le schéma synoptique d'un exemple de réalisation de terminal téléalimenté.
• La figure 3 représente le schéma synoptique plus détaillé de cet exemple de réalisation représenté sur la figure 2.
• La figure 4 représente schématiquement les changement d'état subis par l'exemple de réalisation représenté sur la figure 3.
• La figure 5 représente le schéma synoptique du circuit de mesure d'intensité utilisé dans cet exemple de réalisation représenté sur la figure 2.
• La figure 6 représente le schéma synoptique d'une variante de réalisation du circuit de mesure d'intensité représenté sur la figure 5.

The invention will be better understood and other characteristics will appear with the aid of the description below and the accompanying figures:

• FIG. 1 represents the block diagram of part of an example of local network comprising concentrators and repeaters each comprising an exemplary embodiment of the remote supply device according to the invention.
• FIG. 2 represents the block diagram of a concentrator comprising an exemplary embodiment of the remote power supply device, and the block diagram of an exemplary embodiment of a remote powered terminal.
• FIG. 3 represents the more detailed block diagram of this exemplary embodiment represented in FIG. 2.
• FIG. 4 schematically represents the changes of state undergone by the embodiment shown in FIG. 3.
• FIG. 5 represents the block diagram of the intensity measurement circuit used in this exemplary embodiment represented in FIG. 2.
• FIG. 6 represents the block diagram of an alternative embodiment of the intensity measurement circuit shown in FIG. 5.

FIG. 1 represents the block diagram of part of an example of local network comprising a concentrator 3 and repeaters RP ₁ , ···, RP _M each comprising an exemplary embodiment of the remote supply device according to the invention. It is a local computer network of Ethernet type, which further comprises: a local network server 1; a switch 2; M terminals 4 ₁ to 4 _M , connected to the concentrator 3 respectively via the repeaters RP ₁ , ..., RP _M , because of the distance; and N terminals 5 ₁ to 5 _N , connected directly to the concentrator 3. These terminals are, for example, telephones operating in VolP mode (“Voice over IP” in English, for “packet voice over IP protocol”).

Server 1 is connected to an Internet network 0. It transmits and receives packets according to the TCP / IP protocol. The packets of a given communication are routed through the switch 2 and the concentrator 3 to a terminal, such as the terminal 4 ₁ , the latter being connected to the concentrator 3 through an 8-wire L-type link, with RJ45 connectors. .

FIG. 2 represents in particular the block diagram of an exemplary embodiment of a remote supply device located in the concentrator 3, and of an exemplary embodiment of a terminal, 5 _N , remotely supplied via the link L connecting it to the concentrator 3.

• A1, A2 non utilisée,
• B1, B2 non utilisée,
• C1, C2 utilisée pour la transmission de données vers le réseau, en mode différentiel,
• D1, D2 utilisée pour la transmission de données vers le terminal, en mode différentiel.

The link L has four pairs:

• A1, A2 not used,
• B1, B2 not used,
• C1, C2 used for data transmission to the network, in differential mode,
• D1, D2 used for data transmission to the terminal, in differential mode.

The pairs C1, C2 and D1, D2 are also used in common mode to remotely supply the terminal 5 _N by a phantom circuit.

The concentration 3, includes a remote feeding unit 31 and detection of the presence of a remote power terminal, and a combiner 32. The combiner 32 includes two transformers 33 and 34 transmitting respectively a Tx signal to be sent to a terminal, and an Rx signal received from a terminal. They each have a first winding and a second winding. The first windings are respectively connected to the pairs D1, D2 and C1, C2. They each have a midpoint connected respectively to a output of the remote supply and terminal presence detection unit 31 remotely powered. The second windings are connected to other organs of the concentration 3 which are not shown.

The terminal 5 _N comprises a separator 20 and a DC-DC converter 22 intended to lower the remote supply voltage. The separator 20 comprises two transformers 41 and 40 respectively for transmitting a signal Tx 'to be sent to the concentration 3, and transmitting a signal Rx' received by the terminal 5 _N. They each have a first winding and a second winding. The first windings are connected respectively to pairs D1, D2 and C1, C2. They each have a midpoint. These midpoints provide a DC remote power supply voltage Vr. In this example, the midpoint of the first winding of the transformer 41 constitutes the positive pole of the remote power supply. It is connected by a diode D2 to a positive input of the converter 22. The midpoint of the second winding of the transformer 40 constitutes the negative pole of the remote power supply. It connected directly to a negative input of converter 22.

An identification module 21 is placed in bypass on the two poles of the remote power supply. It allows the unit 31 to recognize that this terminal is remotely powered. The electrical characteristics of the identification module 21 are chosen such that it does not short-circuit the remote supply voltage applied to converter 22, and that it is easily distinguishable from to terminations that are commonly connected to available conductors RJ45 terminals. For example, module 21 consists of a capacity connected between the two remote supply poles. This ability can be constituted by the filtering capacity conventionally placed at the input of a voltage converter. The remote supply device according to the invention is usable regardless of the type of identification module used in the terminals.

• les conducteurs A1, A2 seulement ;
• ou B1, B2 seulement ;
• ou via A1, A2, B1, et B2 simultanément ;
• ou via A1, A2, B1, B2, et le circuit fantôme simultanément ;

selon la puissance nécessaire au terminal.According to an alternative embodiment, instead of remote supply by a phantom circuit, it is possible to remote supply by:

• conductors A1, A2 only;
• or B1, B2 only;
• or via A1, A2, B1, and B2 simultaneously;
• or via A1, A2, B1, B2, and the phantom circuit simultaneously;

depending on the power required by the terminal.

• un circuit de mesure d'intensité 42, ayant une entrée 56 et une sortie 55 pour le courant de téléalimentation, cette dernière étant reliée au point milieu du transformateur 33 ;
• un commutateur 44 ayant trois entrées et une sortie, cette dernière étant reliée à l'entrée 50 du circuit de mesure d'intensité 42
• une capacité C1 en dérivation entre l'entrée 56 et la sortie 55 du circuit 42;
• un générateur 45 de tension alternative de test (fournissant un signal sinusoïdal, de quelques volts, à 10 kilohertz par exemple), ayant une borne reliée au point milieu du transformateur 34 et une autre borne reliée à une première borne d'une résistance R1 ; la seconde borne de cette résistance R1 étant reliée à une première entrée du commutateur 44 ;
• un générateur 46 de tension continue de téléalimentation (de 48V par exemple) ayant une entrée de commande reliée à une sortie CL du circuit de mesure d'intensité 42, une borne négative reliée au point milieu du transformateur 34, et une borne positive reliée à une première borne d'une résistance R3 par une inductance 49 ; la seconde borne de cette résistance R3 étant reliée à une deuxième entrée du commutateur 44 ;
• un générateur 47 de tension continue de test (de 5 volts par exemple), ayant une borne positive reliée au point milieu du transformateur 34 et une borne négative reliée à une première borne d'une résistance R2 ; la seconde borne de cette résistance R2 étant reliée à une troisième entrée du commutateur 44 ;
• un circuit logique 43 ayant : une entrée reliée à la seconde borne de la résistance R1 ; deux entrées reliées respectivement aux bornes de la résistance R2 ; une entrée reliée à une sortie CM du circuit de mesure d'intensité 42 ; et une sortie qui commande le commutateur 44.

FIG. 3 represents the more detailed block diagram of the embodiment 31, of the remote supply device located in the concentrator 3, for a remote supply via a phantom circuit using the common modes on two pairs of data transmission / reception. He understands :

• an intensity measurement circuit 42, having an input 56 and an output 55 for the remote supply current, the latter being connected to the midpoint of the transformer 33;
• a switch 44 having three inputs and an output, the latter being connected to the input 50 of the intensity measurement circuit 42
• a capacitor C1 in derivation between the input 56 and the output 55 of the circuit 42;
• a generator 45 for alternating test voltage (providing a sinusoidal signal, of a few volts, at 10 kilohertz for example), having one terminal connected to the midpoint of the transformer 34 and another terminal connected to a first terminal of a resistor R1; the second terminal of this resistor R1 being connected to a first input of the switch 44;
• a generator 46 of remote power supply voltage (of 48V for example) having a control input connected to an output CL of the current measurement circuit 42, a negative terminal connected to the midpoint of the transformer 34, and a positive terminal connected to a first terminal of a resistor R3 by an inductor 49; the second terminal of this resistor R3 being connected to a second input of switch 44;
• a generator 47 for direct test voltage (of 5 volts for example), having a positive terminal connected to the midpoint of the transformer 34 and a negative terminal connected to a first terminal of a resistor R2; the second terminal of this resistor R2 being connected to a third input of switch 44;
• a logic circuit 43 having: an input connected to the second terminal of the resistor R1; two inputs connected respectively to the terminals of the resistor R2; an input connected to an output CM of the intensity measurement circuit 42; and an output which controls the switch 44.

The output CM of the intensity measurement circuit 42 provides a signal to the logic circuit 43 when the intensity of the remote supply current is greater than the minimum value, 1 mA, which means that the terminal is still logged.

The output CL of the intensity measurement circuit 42 provides a signal to the remote power generator 46 when the intensity of the remote power supply is greater than 350 mA, which means that an anomaly affects the terminal or line, and therefore the remote power supply must be interrupted.

In this example,
R1 = 75 ohms,
R2 = 2 ohms,
R3 = 10 ohms,
C1 = 1 microfarad.

The inductance 49, in series with the generator 46, has a value such that, when the generators 45 and 46 are coupled simultaneously to the remote terminal, attenuation of the AC test signal caused by the generator 46, or negligible. In other embodiments, this function can be filled by means of an active circuit.

The value of C1 is chosen so as to transmit the alternating signal from detection, with negligible attenuation. AC generator voltage 45 and the value of resistance R1 are chosen so as to circulate a test current having a current which is safe for any terminal likely to be connected at the end of the link, especially if it is a non-terminal remotely powered. The DC test voltage supplied by the generator 47 is very lower than the remote supply voltage, to be safe for non-remotely powered terminals. On the other hand, it is insufficient to make start the converter 22 of a remote power terminal. This converter 22 is therefore seen as an open circuit during the DC test.

The intensity measurement device according to the invention can be used whatever or the type of test used to identify the type of terminal.

• Evénement 102 : le module est supérieur à 50 ohms, c'est un circuit ouvert pour le courant alternatif, donc il n'y a aucun terminal connecté au bout de la liaison, le circuit 43 reste dans son état S1 pour continuer ce test en courant alternatif.
• Evénement 101 : le module est inférieur à 50 ohms, il y a un court-circuit au moins pour le courant alternatif, donc il peut y avoir un terminal téléalimentable connecté au bout de la ligne, ou bien un court-circuit entre deux conducteurs de la ligne ; le circuit 43 passe à l'état S2 qui va permettre de discriminer ces deux cas, au moyen d'un test en courant continu, avec une faible tension et une courte durée. Ce courant continu est fourni par le générateur 47. Lors de ce test, le convertisseur 22 du terminal présente une résistance élevée parce qu'il reçoit une tension d'entrée insuffisante pour pouvoir démarrer.

Le test réalisé dans l'état S2 conduit à deux événements possibles :

• Evénement 105 : le module de l'impédance est supérieur à 50 ohms, c'est un circuit ouvert pour le courant continu, donc il n'y a aucun terminal classique connecté au bout de la liaison ; c'est un terminal téléalimentable ou un terminal à alimentation locale sécurisé par téléalimentation. Le circuit 43 passe dans un état S4 pour téléalimenter ce terminal tout en continuant le test en courant alternatif afin de détecter une déconnexion éventuelle du terminal qui a été détecté.
• Evénement 104 : le module de l'impédance est inférieur à 50 ohms, donc il y a un court-circuit pour le courant continu dans le terminal ou sur la liaison ; il y a donc un terminal classique (ayant une terminaison comportant un court-circuit) ou bien il y a un court-circuit accidentel dans lequel il ne faut pas envoyer le courant de téléalimentation ; le circuit 43 passe à l'état S3 qui va permettre de surveiller une éventuelle disparition de ce court-circuit.

FIG. 4 schematically represents the change of state undergone by the exemplary embodiment 31 represented in FIG. 3. During startup, it is in a state S1 for carrying out an AC test for detecting the presence of a terminal remotely powered: the logic circuit 43 actuates the switch 44 to connect only its first input to its output. The remote supply voltage is not applied to the link L, so there is no risk for a conventional terminal. Switch 44 transmits alternating current. The logic circuit 43 compares the value of the alternating voltage present on the second terminal of the resistor R1 with a threshold value corresponding to a module of impedance equal to 50 ohms for example. There are two possible events:

• Event 102: the module is greater than 50 ohms, it is an open circuit for alternating current, so there is no terminal connected at the end of the link, circuit 43 remains in its state S1 to continue this test in alternating current.
• Event 101: the module is less than 50 ohms, there is a short circuit at least for the alternating current, so there may be a remote power terminal connected at the end of the line, or a short circuit between two conductors line ; the circuit 43 goes to state S2 which will make it possible to discriminate these two cases, by means of a DC test, with a low voltage and a short duration. This direct current is supplied by the generator 47. During this test, the converter 22 of the terminal has a high resistance because it receives an insufficient input voltage to be able to start.

The test carried out in state S2 leads to two possible events:

• Event 105: the impedance module is greater than 50 ohms, it is an open circuit for direct current, so there is no conventional terminal connected at the end of the link; it is a remote power terminal or a locally powered terminal secured by remote power. The circuit 43 goes into a state S4 to remotely supply this terminal while continuing the AC test in order to detect a possible disconnection of the terminal which has been detected.
• Event 104: the impedance module is less than 50 ohms, so there is a short circuit for direct current in the terminal or on the link; there is therefore a conventional terminal (having a termination comprising a short circuit) or else there is an accidental short circuit in which the remote supply current must not be sent; circuit 43 goes to state S3 which will make it possible to monitor a possible disappearance of this short circuit.

In the state S3, the circuit 43 does periodically, for example once per second, a short-term, low-voltage test to detect the disconnection of a conventional terminal. Unit 31 provides direct current of sufficiently low intensity and duration to test for the presence of a terminal classic without risking damaging it. Circuit 43 operates switch 44 to connect only its second input to its output, for a period of 150 milliseconds only. After 100 milliseconds (necessary for a any capacity has time to charge), circuit 43 measures the voltage across R2. If this voltage is zero, the circuit is open for the direct current. During this test, the remote supply voltage is not applied to the L link. The voltage applied for the test is 5 volts in this example. There is therefore no risk for a terminal. Logic circuit 43 compare the value of the DC voltage measured on the terminals of the resistor R2 with a single threshold value, corresponding for example to a resistance equal to 50 ohms.

This test is repeated until the value becomes greater than 50 ohms (Event 106): Circuit 41 then returns to state S1 to detect the possible connection of a remote power terminal.

• une éventuelle déconnexion du terminal téléalimentable qui a été détecté,
• ou une éventuelle défaillance de la liaison ou du terminal, créant un court-circuit pour le courant continu.

Le circuit 43 actionne le commutateur 44 pour relier sa troisième entrées à sa sortie. Un courant de téléalimentation est donc fourni à la liaison L. Un courant continue circule dans le circuit de mesure d'intensité 42 tant que le terminal téléalimentable reste connecté au bout de la ligne L. Le circuit 42 surveille l'intensité par rapport aux valeurs de seuil 1 mA et 350 mA. Pendant l'état de S4, il peut y avoir deux événements :

• Evénement 107 : l'intensité devient inférieure à 5 mA, donc le terminal téléalimentable a été déconnecté ; le circuit 43 repasse à l'état S1. La tension de téléalimentation n'étant plus appliquée à la liaison, un autre terminal quelconque peut donc être branché en toute sécurité.
• Evénement 108 : l'intensité devient supérieure à 350 mA, donc il y a une anomalie, soit sur la liaison, soit dans le terminal. Le circuit 43 passe dans un état S5 où il arrête la téléalimentation pendant 30 secondes, par exemple, pour éviter toute détérioration par le courant de téléalimentation. Puis il repasse à l'état S1 où les tests réalisés précédemment sont réitérés.

In the state S4, the unit 31 supplies a remote supply current to the remote supply terminal which has been detected, and monitors the appearance of two possible events

• a possible disconnection of the remote supply terminal which has been detected,
• or a possible link or terminal failure, creating a short circuit for direct current.

The circuit 43 actuates the switch 44 to connect its third inputs to its output. A remote supply current is therefore supplied to the link L. A continuous current flows in the intensity measurement circuit 42 as long as the remote supply terminal remains connected at the end of the line L. The circuit 42 monitors the intensity with respect to the values 1 mA and 350 mA threshold. During the state of S4, there can be two events:

• Event 107: the current becomes less than 5 mA, therefore the remote power terminal has been disconnected; circuit 43 returns to state S1. Since the remote supply voltage is no longer applied to the link, any other terminal can therefore be connected securely.
• Event 108: the current becomes greater than 350 mA, so there is an anomaly, either on the link or in the terminal. The circuit 43 goes into a state S5 where it stops the remote supply for 30 seconds, for example, to avoid any deterioration by the remote supply current. Then it returns to state S1 where the tests previously carried out are repeated.

• un circuit résistif non linéaire 50 constitué d'une résistance R10 de 50 ohms, d'une résistance R11 de 1 ohm, d'un transistor à effet de champ T, et un comparateur à hystérésis 52 ayant une valeur de seuil égale à 50 mV pour une tension descendante, et une valeur de seuil égale à 2,5 V pour une tension montante, ces deux valeurs correspondant à un troisième seuil d'intensité compris entre les deux seuils d'intensité à surveiller (1 et 350 mA) et égal à 50 mA ;
• un comparateur 51 ayant deux entrées reliées respectivement aux bornes de la résistance R10, et une sortie fournissant un signal logique lorsque la chute de tension sur la résistance R10 dépasse une valeur de seuil de tension égale à 50 mV ;
• un comparateur 53 ayant deux entrées reliées respectivement aux bornes de la résistance R11, et une sortie constituant la sortie CL et fournissant un signal logique lorsque la chute de tension sur la résistance R11 dépasse une valeur de seuil de tension égale à 350 mV ;
• et une porte logique OU 54 ayant deux entrées reliées respectivement aux sorties des comparateurs 51 et 52, et une sortie constituant la sortie CM.

FIG. 5 represents the block diagram of the intensity measurement circuit 42 used in this exemplary embodiment 31. It comprises:

• a non-linear resistive circuit 50 consisting of a resistor R10 of 50 ohms, of a resistor R11 of 1 ohm, of a field effect transistor T, and a hysteresis comparator 52 having a threshold value equal to 50 mV for a falling voltage, and a threshold value equal to 2.5 V for a rising voltage, these two values corresponding to a third intensity threshold comprised between the two intensity thresholds to be monitored (1 and 350 mA) and equal at 50 mA;
• a comparator 51 having two inputs connected respectively to the terminals of the resistor R10, and an output providing a logic signal when the voltage drop on the resistor R10 exceeds a voltage threshold value equal to 50 mV;
• a comparator 53 having two inputs connected respectively to the terminals of the resistor R11, and an output constituting the output CL and providing a logic signal when the voltage drop on the resistor R11 exceeds a voltage threshold value equal to 350 mV;
• and an OR logic gate 54 having two inputs connected respectively to the outputs of the comparators 51 and 52, and an output constituting the output CM.

A first terminal of the resistor R10 is connected to the input 56 of the non-linear resistive circuit 42. Its second terminal is connected to output 55 of the non-linear resistive circuit 42. A first terminal of the resistor R11 is connected to input 56 of the non-linear resistive circuit 42. Its second terminal is connected at the output 55 of the non-linear resistive circuit 42 by the transistor T. The gate of control of transistor T is connected to the output of comparator 52.

Comparator 52 has two inputs connected respectively to the terminals of resistance R10, and an output providing a logic signal passing from value 0 at value 1 when the voltage drop on resistor R10 exceeds one threshold value of 2.5 V, and going back from the value 1 to the value 0 when the voltage drop on resistor R10, which is then in parallel with the resistance R11, becomes again below another threshold value equal to 50 mV.

The transistor T is therefore on when the voltage between the inputs of the comparator 52 becomes greater than 2.5 V, and it is again blocked when the voltage between the inputs of comparator 52 again becomes less than 50 mV. The transistor T is used as electronic switch to connect the resistance R11 in parallel with the resistance R10, so as to decrease the resistance of the resistive circuit 50 from 50 ohms to about 1 ohm when the current intensity remote power supply becomes higher than the third intensity threshold (close to 50mA); then increase it from about 1 ohm to 50 ohms when the intensity of the remote supply current becomes less than this third intensity threshold. In effect, the output of comparator 52 provides a logic signal of value 1 as soon as the voltage drop on the resistor R10 = 50 ohms exceeds a threshold value 2.5 V, i.e. as soon as the current is greater than 50 mA. But this signal logic returns to the value 0 when the voltage drop on resistor R10 in parallel with resistor R11 (i.e. about 1 ohm) becomes less than the threshold value 50 mV; that is to say as soon as the intensity is less than 50 mA.

The OR gate 54 provides a logic signal of value 1 indicating the continued presence of the terminal, both in the event that the remote supply current through resistance R10 only, only in the case where it crosses resistors R10 and R11 in parallel. When the intensity is less than 50 mA, OR gate 54 provides a logic signal of value 1 from that the comparator 51 has detected an intensity greater than 1 mA in the resistance R10 = 50 ohms only. Comparator 52 controls the setting parallel of resistors R10 and R11 when the intensity exceeds 50 mA. Therefore the comparator 51 no longer provides a logic signal of value 1 because the fall in voltage is only 50 mV for 50 mA. The OR 54 door nevertheless provides a logic signal of value 1 because the comparator 51 detects an intensity greater than 50 mA in resistors R10 and R11 in parallel, equivalent to a resistance of 1 ohm.

FIG. 6 represents the block diagram of an alternative embodiment 42 ′ of the intensity measurement circuit shown in FIG. 5. It includes a comparator 51 ′, a comparator 53 ′, and an OR gate 54 ′ similar to the comparator respectively 51, to comparator 53, and to OR gate 54, and which respectively have the same functions. The non-linear resistive circuit 50 is replaced by a non-linear resistive circuit 50 '. The comparator 51 'is also part of this non-linear circuit 50'.

• une résistance R10' de 50 ohms ;
• une résistance R11' de 1 ohm ;
• un transistor à effet de champ T' ;
• un comparateur 60 (sans hystérésis) ayant deux entrées reliées respectivement aux bornes de la résistance R10', et une sortie fournissant un signal logique lorsque la chute de tension sur la résistance R10 dépasse une valeur de seuil de tension égale à 2,5 V correspondant à un troisième seuil d'intensité compris entre les deux seuils d'intensité à surveiller (1 et 350 mA) et égal à 50 mA ;
• un comparateur 51' ayant deux entrées reliées respectivement aux bornes de la résistance R10', et une sortie fournissant un signal logique de valeur 1 lorsque la chute de tension sur la résistance R10' dépasse une valeur de seuil de tension égale à 50 mV correspondant au seuil d'intensité égal à 1 mA lorsque le courant de téléalimentation traverse la résistance R10' seulement, et correspondant au seuil d'intensité égal à 50 mA lorsque le courant de téléalimentation traverse la résistance R10' et la résistance R11' en parallèle ;
• et une bascule 61 ayant une entrée de mise à 1 reliée à la sortie du comparateur 60, une entrée de remise à zéro reliée à la sortie du comparateur 51', et une sortie reliée à la grille de commande du transistor T', et à une entrée de la porte OU 54'.

The circuit 50 'further includes:

• a resistor R10 'of 50 ohms;
• a resistance R11 'of 1 ohm;
• a field effect transistor T ';
• a comparator 60 (without hysteresis) having two inputs connected respectively to the terminals of the resistor R10 ', and an output providing a logic signal when the voltage drop on the resistor R10 exceeds a voltage threshold value equal to 2.5 V corresponding a third intensity threshold between the two intensity thresholds to be monitored (1 and 350 mA) and equal to 50 mA;
• a comparator 51 'having two inputs respectively connected to the terminals of the resistor R10', and an output providing a logic signal of value 1 when the voltage drop on the resistor R10 'exceeds a voltage threshold value equal to 50 mV corresponding to the intensity threshold equal to 1 mA when the remote supply current crosses the resistor R10 'only, and corresponding to the intensity threshold equal to 50 mA when the remote supply current crosses the resistor R10' and the resistor R11 'in parallel;
• and a flip-flop 61 having a reset input connected to the output of comparator 60, a reset input connected to the output of comparator 51 ', and an output connected to the control gate of transistor T', and a door entrance OR 54 '.

A first terminal of the resistor R10 'is connected to the input 56 of the non-linear resistive circuit 42 '. Its second terminal is connected to output 55 of non-linear resistive circuit 42 '. A first terminal of resistance R11 'is connected to the input 56 of the non-linear resistive circuit 42 '. Its second terminal is connected at the output 55 of the non-linear resistive circuit 42 'by the transistor T'. The transistor T 'is used as an electronic switch to connect the resistor R11' in parallel with the resistance R10 ', so as to decrease the resistance of the resistive circuit 50 'from 50 ohms to about 1 ohm when the current of remote power supply becomes higher than the third intensity threshold (50mA); then to increase it from 1 ohm to 50 ohms when the current intensity of remote power supply falls below this third intensity threshold.

The flip-flop 61 is set to 1 when the comparator 60 detects that the current exceeds 50 mA in the resistor R10, and it is reset to zero when the comparator 51 'detects that the intensity becomes less than 50 mA in resistor R11 'in parallel with resistor R10'.

The OR gate 54 'provides a logic signal of value 1 indicating the continued presence of the terminal, both in the event that the remote feed current through resistance R10 'only, only in the case where it crosses resistors R10 'and R11' in parallel. When the intensity is less than 50 mA, OR gate 54 'provides a logic signal of value 1 from that the comparator 51 'has detected an intensity greater than 1 mA in the resistance R10 '= 50 ohms only. Comparator 60 controls the setting of 1 flip-flop 61, and therefore the paralleling of resistors R10 'and R11', when the current exceeds 50 mA. Then the comparator 51 'no longer provides a signal logic value 1 because the voltage drop is only 50 mV for 50 mA. The OR gate 54 'nevertheless provides a logic signal of value 1 because the output of flip-flop 61 continues to supply a logic signal of value 1.

The scope of the invention is not limited to the embodiments described above. The device having a nonlinear resistance can include a non-linear component, of known type, passive or active, the resistance decreases continuously as the intensity increases, the two values of voltage threshold being chosen according to the characteristic of the component and of each intensity threshold value.

Claims (5)

A remote supply device for a terminal in a telecommunications network, this remote supply device comprising a measurement device for determining at least if the intensity of the remote supply current is greater than a first intensity threshold value, the intensity possibly take a value much higher than this first threshold value; this measuring device comprising: a resistive circuit (50) through which the remote supply current flows, and means (51) for comparing the voltage across this resistive circuit (50) with a first voltage threshold value, characterized in that this resistive circuit (50) has a variable resistance as a function of the intensity which passes through it, this resistance being lower when the intensity is much greater than the first intensity threshold value. Device according to claim 1, comprising a measuring device for determining whether the intensity of the remote power supply current is greater than a first intensity threshold value and for determining whether this intensity is greater than a second intensity threshold value, which is higher than the first; this measuring device further comprising means (53) for comparing the voltage across this resistive circuit (50) with a second voltage threshold value;
characterized in that this resistive circuit (50) has a variable resistance as a function of the intensity flowing through it, this resistance being lower when the intensity is close to the second intensity threshold value, than in the vicinity of the first intensity threshold value. Device according to claim 2, characterized in that this resistive circuit (50; 50 ') comprises: a first measurement resistor (R10; R10 '), a second measurement resistor (R11 in parallel with R10; R11 'in parallel with R10') having a value lower than that of the first (R10; R10 '), and a switching device (52, T; 61, T ') for alternately: put the first resistor (R10; R10 ') in series in the remote supply circuit, if the switching device (52, T; 61, T') detects that the intensity is less than a third intensity threshold value, which is included in the interval between the first and the second intensity threshold value; or put the second resistor (R11 in parallel with R10; R11 'in parallel with R10') in series in the remote supply circuit, if the switching device (52, T; 61, T ') detects that the intensity is greater at the third threshold value. Repeater characterized in that it comprises a remote supply device according to one of claims 1 to 3. Concentrator characterized in that it comprises a remote feeding device according to one of claims 1 to 3.

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